Very weird nugget to share. Now I am a very fussy person when it comes to animation lag, stutter and OS delays. Previously I updated OTA and was absolutely annoyed by the hassles, like many others. Tonight I had a hunch and instead did the full update via iTunes. It's running without issue at all. Now I don't know if the phone goes through some kind of clean up process that can take over a day, but the difference is alarming. Very happy iOS 9 user now.